A power line communications technology refers to a communication manner in which a power line is used to transmit data and a media signal. According to the technology, a signal is loaded into a current, then the current is sent to a power line communications device by using the power line, and the power line communications device separates the signal that is loaded into the current from the current and sends the signal to a terminal device. However, an existing power line communications device can send a separated signal to a terminal device only by using a network cable or in a WiFi signal manner, and cannot send the separated signal to the terminal device by using a USB interface.